The purpose of this invention is to allow a system called Dynamic Time Division Multiple Access (D-TDMA) as hereafter described in this Background section to properly function in a radio frequency or other wireless network.
One of the goals of asynchronous data communication is to maximize the use of the available bandwidth on media by allocating bandwidth on a “first come, first served basis”. This trait is especially valuable in a wireless radio frequency network where bandwidth can be hard to obtain. Another advantage of this method is that it typically provides low latencies of communications when the media use is not high. A deficiency of asynchronous communication is that while it can provide a “best effort” towards routing packets to their desired destination, it cannot provide a guaranteed level of service i.e. a commitment that a packet will arrive at the desired station within a given timeframe.
A TDMA protocol can be used to provide a guaranteed level of Quality of Service (QoS) by allocating communications link time to particular stations rather than by allocating bandwidth on a “first come, first served basis”. FIG. 1 shows an example of a “superframe” made up of seven slots dedicated to particular stations. The beacon is a slot reserved for the media coordinator to synchronize all station's clocks and to advise all stations of the media allocation schedule. The problem with this protocol is that it is not spontaneous and dynamic, i.e. it requires the users to set up a service schedule with the media coordinator prior to their usage and requires the users to advise the media coordinator when the service is not required. Since the actual bandwidth requirements of many stations cannot be known in advance, a station is forced to request a “worst case” estimation of bandwidth required, i.e. the largest amount that it might need. This practice leads to inefficient use of bandwidth.
The intent of a D-TDMA algorithm is to provide the high Quality of Service (QoS) of the TDMA protocol to a communications link while providing a mechanism to use excess instantaneous bandwidth. In this manner time bounded allocations of bandwidth are made to stations to support their necessary QoS levels. Should a station not required the level of bandwidth allocated it will cease transmission and another station may detect that cessation and start its transmission earlier than its allocation. In this manner excess bandwidth is not “wasted” due to non-use by the allocated station. The details of this detection is to observe the media for activity, if it has been inactive for an amount of time named a “mini-slot” it will deem the media available for its use. FIG. 2 illustrates this concept. In this example the station which was allocated slot 2 did not need the full time slot so it ceased transmission. Another station sensed this vacancy after a mini-slot and used up the remaining time designated as slot 2a. 